## Performance metric

The performance metric for comparing the RT Boxes is the average execution time per core. For the RT Box 1 and the single core operation of RT Boxes 2 and 3, this means only one core is calculating the complete model. In the case of RT Boxes 2 and 3’s multicore operation, the total average execution time is calculated from the average execution time of each of the three available simulation cores.

## Simulation model

To compare the performance of the RT Boxes, a modular multilevel converter (MMC) model is used. With new Task Frames on version 4.4 of PLECS, the user can split the system into different parts to run them on a single or multiple cores, as well as easily scale the number of cells in the converter. The model is open-loop controlled with the switching signals generated by another RT Box.

The MMC has a configurable number of sub-cells per arm that all contain a full-bridge, a DC capacitor and a non-ideal DC voltage input. Given a number of cells (N) per arm, the total number of switching devices in this converter is 24 x N.

RT Boxes 1 and 2 are able to simulate up to 5 cells with its 32 digital inputs. RT Box 3 is able to simulate up to 10 cells per arm as it has 64 digital inputs.

## Results

There is a clear performance gain with the 1.5 GHz processor in RT Boxes 2 and 3 over the 1 GHz processor in RT Box 1. Another significant performance gain is achieved by running the plant model on different simulation cores of RT Boxes 2 and 3.